Problem: $ { {3} \times \left[\begin{array}{rr}{0} & {4} \\ {4} & {-1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{3}\times{0} & {3}\times{4} \\ {3}\times{4} & {3}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{0} & {12} \\ {12} & {-3}\end{array}\right]}$